Sir camerart . . . . .
If you came into this session knowing " nuttin ".. . . . . . rejoice . . . .as when you leave, you should leave knowing a little more than . . . " nuttin ".
So o o o o o o . . . . . you seem to have yourself a
DREMEL rotary motor tool wannabe there . . .hunh h h h ?
First, do you have any more relevant info on the unit, as to whether it stopped or will not run or runs full speed, smoked, or was cutting in and out intermittently before failing ?
I see your second photo now, and that confirms that you are cognizant as to what some of the components are. I had already started on a blowup mark-up of what you had posted initially . . .it seems to work better for marking up..
I was also perceiving of the
YELLOW circles as being the units speed control pot. The
BLUE circles, as being a very low value resistor between those connections , to get some max current limiting , as well as cross power B+ connection to the other side of the board
All of the deteris on the board along with not exactly being in macro focus, inhibited my seeing if there was a dimple on the IC where I have inserted the
YELLOW semicircle index. ( Confirm)
That then would verify my
PROPER assignment / placement of the Pin 1 of the IC.
Now tell me that you do / did an AWFUL lot of plastic or epoxy grinding with this unit . . . . . by all of the surfactal chaff presence.
I sort of expect that IC to be either a comparator or op amp that is being pressed into application as a variable pulse width generator / driver to feed the gate of the power FET.
In my " Reading " of the PCB foil, we see that the FET's Drain-Source is completeing the negative power leg of the DC motor path to ground.
I also am skeptical of the fault being with the IC
Firstly . . . . is your battery pack presently charged up to FULL current / power capability or OOOOOOOOMMMMMMMPPPPHHHH !
If that is being of no question, then the problem of a commutator segment(s) or brush erosion within the DC motor would be a consideration.
Particularly if the unit has received LOTS of use.
Second main consideration would be the failure of the POWER FET / power electronic switch. Should it be shorted from D-S the unit would be running continously at full speed.
If bad in its second manner . . . . . it would not be responding to the variable drive being applied to its GATE, to enact D-S conductivity to run the motor..
what to do . . .what to do . . .WHAT TO DO . . . .?
Initially, see if you can enact a connection of the battery power pack to the controller boards two side contact tabs via the use of two test leads witn their paired clip on connectors, between the B+ and B- side spring connectors.
If by advancing the speed pot and the unit is then found inoperative, taking the end tip of the blade of a mini pocket sized STANDARD screwdriver blade and shorting across the D-S of the power FET should have the unit running at full speed for that instance of contact. That means motor health and its series arranged brush-field***-rotor continuity for operation is complete. (*** unless its using a permanent magnet surround, instead of a field winding.)
Then try a 100 ohm resistor, temporarily touched from Drain to Gate to see if the motor responds.
If that works . . .only
then, do we start questioning the IC.
On the IC . . . . Harald has done better than I . . . if he found any mention of that SY069 amongst the Ali Express IC supply circles.
What I am seeing . . .
In reading that unit with my assigned indexing of pin 1.
I see R9-R6-R7-speed pot and the sole C1 timing capacitor relating to the variable pulse width drive generator circuitry.
That circuitry is all being within the
RED indexed boundaries.
I see
pin 2 going over to be the chips
ground connection and
pin 8 working its way up a foil path to a 300 ohm R4 to get
Vcc power for the chip.
Probably, there is the forementioned low value power resistor between the
BLUE dots.
I
HIGHLY suspicion that the nearby R5 resistor, is coupling the variable chip drive into the Gate of the power FET.
ASIDE . . . .rather than overheating of the FET, SURELY, the adljunct discoloration I am seing is just from sloppy rosin residue , being left uncleaned from the board, at factory install time..
Over to the right, I inserted what would be the use of a typical 555 for a motor control circuit of a power FET, but one can see that the pin outs don't agree for
that common IC . . . . but you can see, how the other major components are relating to your units design.
Waiting for your feedback from your observations and tests.
Photo Referencing . . . . .
https://i.imgur.com/KIaHJcI.jpg
73's de Edd . . . . .
With my old man I never got no respect. As a kid, I once asked him,
"How can I get my kite in the air?"
He told me to run off a cliff.